The present invention relates to a power-assistance method for uphill maneuvers for a vehicle.
More particularly it relates to a method for aiding in uphill starting of a motor vehicle having a manual or automatic gearbox.
On certain vehicles, the automobile manufacturers are offering a power-assisted parking brake.
By reason of its relatively high cost compared with the traditional parking brake solution, this power-assisted parking brake must provide performance that adds value for the customer.
To add value to this system, the manufacturers have therefore decided to associate therewith a power-assistance function for uphill maneuvers and especially power assistance for uphill starting (or pulling away), wherein the principle is to release the brakes on the non-driving wheels as soon as the torque transmitted by the engine to the driving wheels is sufficient to compensate for the inclination effect of the slope.
Such devices are already known.
In this regard, document GB 2376990 proposes a control module for a power-assisted parking brake device for a motor vehicle provided with a manual gearbox, which releases the force applied to the parking brake when it receives signals indicating to it, on the one hand, a positive displacement of the accelerator pedal and, on the other hand, that the position of the clutch pedal has reached its bite point. The instant at which the device releases the brake also depends on the clutch-pedal depression velocity, on the gear ratio engaged and on the slope on which the vehicle user is located.
This device has the disadvantage of being sensitive to pitching of the body during a stop, for example due to the movements of passengers, or to pitching of the vehicle when it pulls away.
In fact, before the brakes are released, the vehicle has a tendency to rise, the wheels remaining immobile as long as their movement is prevented by the brake, despite the torque being applied to them. One adverse consequence is delayed pull-away of the vehicle, since the calculated torque transmitted to the clutch is falsified by the data transmitted by the inclination sensor.
To avoid this phenomenon, a low-pass filter, for example, may be introduced to filter the noise and the high-frequency components of the sensor. However, this is not sufficient if the estimate of the transmitted torque is not precise.